scoped-composable-shadows-the-top-level-one

name

scoped-composable-shadows-the-top-level-one

description

Inside a layout scope, a scope-extension composable of the same name wins over the top-level one — silently, since both compile — so a call written for the plain version gets the scoped version's defaults and layout behaviour; covers fully qualifying to force the top-level one, `this@Scope.` to force the scoped one, and why outer scopes still apply from inside a nested layout. Use when an appear/disappear animation expands or collapses its parent instead of fading in place, when a composable behaves differently after being moved into a column or row, or when a call resolves to an overload you did not choose.

The scoped overload shadows the top-level one

Several toolkit composables ship as a top-level function and as extensions on the layout scopes. The extensions differ in their default transitions and in how the element participates in the parent layout. Kotlin prefers an extension on an implicit receiver over a plain top-level function, so inside a column or a row the scoped one wins by default — with no warning, because the call compiles.

// adapted — forcing the top-level overload; the visibility condition is shortened
androidx.compose.animation.AnimatedVisibility(
    visible = isVideo && watchVideo,
    modifier = Modifier.align(Alignment.Center),
) { … }

Traps

Outer scopes are still implicit receivers inside a nested layout. The shadowed call above sits in a Box — but that box is inside a column, and the column's scope is still in scope, so the column extension is what an unqualified call resolves to. Being "inside a Box" is not protection; there is no box-scoped overload to take precedence.

The symptom is a layout behaviour, not an error. The scoped variants default to expanding and shrinking along the parent's axis, so the element pushes its siblings while it appears instead of fading in place. Read as an animation bug ("the column jumps when the video starts"), it sends people looking at the transition parameters rather than at which function ran.